High power lasers have become an important technology for weapons, medical uses, and research. These lasers typically use a beam of particles, such as electrons, atoms, molecules, or ions. The particles are pumped to higher energy states, preferably “meta-stable states.” The energy stored in the meta-stable state can then be extracted in the form of highly coherent laser light.
Several pumping mechanisms have been proposed. Argon ion lasers have been suggested in which a gas discharge is electrically formed and the discharge is confined by an axial magnetic field. (See, e.g., U.S. Pat. No. 4,847,841.) In some cases, the magnetic field is generated by more than one winding to produce fields of opposite polarity. (See, e.g., U.S. Pat. No. 4,974,228.)
Ion lasers normally employ RF energy or glow discharge to excite ions to a higher energy state and an axial magnetic field to confine the excited medium. (See, e.g., U.S. Pat. No. 5,048,032.) Separate power stages that are out-of-phase can be used to provide multi-phase excitation. In another type of pumping scheme, two electron beams traveling with an ion beam achieve and maintain ionization and the required energy states for the ion beam. (See, e.g., U.S. Pat. No. 6,097,740.)
In the case of free-electron lasers, magnetic fields are often used to accelerate a high-energy beam of electrons normal to the beam direction. Stimulated emission results from the acceleration.
One of the disadvantages of many previous schemes is the need for high power to pump the laser medium. If the input power could be reduced, a higher efficiency device would result.